The present application claims priority under 35 U.S.C. xc2xa7119 to Japanese Patent Application No. 2001-216518, filed on Jul. 17, 2001, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a personal watercraft on which an engine with a supercharger is mounted, and particularly to an oil supply passage through which oil is supplied to the supercharger.
2. Description of Background Art
Two-cycle engines have generally been used to power personal watercraft. However, to meet recent requirements to reduce environmental pollution, increasing use has been made of four-cycle engines.
Unfortunately, the output of a four-cycle engine is less than that of a two-cycle engine with the same displacement. To compensate for this insufficient output, consideration has been given to mounting a supercharger on these four-cycle engines. For example, the present applicant has already proposed, in Japanese Patent Laid-Open No. 2001-146197, a personal watercraft on which a four-cycle engine with a supercharger is mounted.
In this personal watercraft, as shown in FIGS. 11 and 12, a four-cycle engine 2 with a supercharger 3 is mounted in a watercraft body 1. The supercharger 3 is disposed on a rear side of the engine 2, and an oil tank 5 is disposed on a front side of the engine 2.
As shown in FIG. 13, an oil pump 4 is provided on a front portion of the engine 2 at a position under the oil tank 5. Oil press-fed from the oil pump 4 is supplied to a main gallery 2a of the engine 2 via piping 6d, an oil filter 6, and piping 6e, and is then supplied from the main gallery 2a to respective components of the engine 2.
Oil is also supplied from the main gallery 2a to a bearing portion 3a of the supercharger 3 via an oil passage 2d formed in a lower bearing portion 2c of a crankshaft 2b, an oil passage 2f formed in an upper bearing portion 2e of the crankshaft 2b, and piping 2g. 
The oil, which has been used for lubricating the bearing portion 3a of the supercharger 3 is recovered, via piping 3b, to an oil pan 2i provided in a lower portion of the engine 2, and is recovered from piping 6a to the oil tank 5 via the oil pump 4.
According to the above-described personal watercraft in which the supercharger 3 is disposed on the rear side of the engine 2 and the oil tank 5 is disposed on the front side of the engine 2, the problem of having the oil stored in oil tank 5 being heated by the supercharger 3 is eliminated.
Another problem occurs however, in the above-described related art personal watercraft. Since oil is supplied from the main gallery 2a to the bearing portion 3a of the supercharger 3 via the oil passage 2d formed in the lower bearing portion 2c of the crankshaft 2b, the oil passage 2f formed in the upper bearing portion 2e of the crankshaft 2b, and the piping 2g, it takes more time than is desirable for oil to be supplied to the supercharger 3 after starting the engine 2.
As a result, it is difficult to ensure a speedy, positive operation of the supercharger.
An object of the present invention is to solve the above-described problem and to provide a personal watercraft on which an engine with a supercharger is mounted, which is capable of ensuring a speedy, positive operation of the supercharger.
To achieve the above object, the present invention provides a personal watercraft on which an engine with a supercharger is mounted, having an engine for driving a jet propelling pump is provided in a watercraft body formed by a hull and a deck in such a manner as to extend in a length direction of the watercraft body, a supercharger is provided in a longitudinal direction of the engine; and an oil supply passage for communicating between the supercharger and an end portion of a main gallery of oil provided in parallel to a crankshaft of the engine.
Further, the present invention provides an oil pump on a portion, on a front side of the watercraft body, of the engine and the supercharger is provided on a portion, on a rear side of the watercraft body, of the engine; and the supercharger and a rear end portion of the main gallery are communicated to each other via the oil supply passage.
In addition, in the present invention, the oil supplied to the supercharger is used for lubricating a bearing portion of the supercharger, and the oil is supplied to an oil jacket formed in a bearing casing to cool the bearing casing. An oil outlet in the supercharger is disposed at a position higher than an oil level at the time of stoppage of the engine.
Moreover, the engine of the present invention is a dry sump engine, an oil tank is provided on an extension of a crankshaft of the engine, and a one-way valve is interposed in an oil return passage communicated to the oil outlet in the supercharger.
The present invention as described above provides the following functions and effects.
As mentioned, the engine for driving the jet propelling pump is provided in the watercraft body formed by the hull and the deck in such a manner as to extend in a length direction of the watercraft body, and the supercharger is provided in a longitudinal direction of the engine; and the supercharger and an end portion of the main gallery of oil provided in parallel to the crankshaft of the engine communicate with each other via the oil supply passage. As a result, oil is supplied from the end portion of the main gallery to the supercharger directly via the oil supply passage. Accordingly, the time required to supply oil to the supercharger after start of the engine is shortened, and hence, a speedy, positive operation of the supercharger can be ensured.
In the related art, one end portion of the main gallery must be closed by a plug (see reference numeral 2p in FIG. 13). By contrast, with configuration of the engine and supercharger used in the present invention, it is possible to eliminate the need for such a plug.
The oil pump of the present invention is provided on a portion, on the front side of the watercraft body, of the engine, and the supercharger is provided on a portion, on the rear side of the watercraft body, of the engine. Further, the supercharger and a rear end portion of the main gallery communicate with each other via the oil supply passage. As a result, it is possible to readily supply oil to the supercharger disposed on the rear side of the engine.
With the configuration of the present invention, oil supplied to the supercharger is used for lubricating the bearing portion of the supercharger, and also the oil is supplied to the oil jacket formed in the bearing casing to cool the bearing casing. As a result, it is possible to use the oil supplied to the supercharger not only for lubricating the bearing portion of the supercharger, but also for cooling the bearing casing.
In the case of lubricating the bearing portion of the supercharger and cooling the bearing casing by using the oil supplied to the supercharger, to readily supply a large amount of oil is required, as compared with the related art personal watercraft.
However, according to the personal watercraft of the present invention, since oil is supplied from the end portion of the main gallery to the supercharger directly via the oil supply passage, a large amount of oil can be readily supplied to the supercharger
Further, with in the present invention, the oil outlet in the supercharger is disposed at a position higher than an oil level at the time of stoppage of the engine. As a result, when the operation of the engine is stopped, oil in the supercharger is readily discharged via the oil outlet.
If oil remains in the supercharger at a high temperature immediately after the engine is stopped, the remaining oil is likely to be carbonized. If this occurs, the entire oil circulating in the engine is likely to deteriorate. The present invention, however, solves this problem, by providing a means by which oil in the supercharger is readily discharged via the oil outlet when the engine is stopped. Accordingly, the amount of oil remaining in the supercharger after the engine is stopped is made as small as possible, thus reducing the deterioration of the entire oil circulating in the engine.
As described earlier, the engine of the present invention is a dry sump engine, and the oil tank is provided on an extension of the crankshaft of the engine. As a result, it is possible to lower an oil level at the time of stoppage of the engine. This, in turn, makes it possible to more readily discharge oil remaining in the supercharger from the oil outlet, and hence to more effectively reduce the deterioration of the entire oil circulating in the engine.
Further, a one-way valve is interposed in the oil return passage communicating with the oil outlet in the supercharger. As a result, it is possible to eliminate the problem that when the personal watercraft is turned over, oil counter flows and remains in the supercharger which still has a high temperature.
This feature helps further to prevent carbonization of oil, and hence to more certainly reduce the deterioration of the entire oil circulating in the engine.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.